The invention concerns wireless local area networks and the communication between the devices forming such a network. More specifically, the present invention relates to a communication scheme which allows a first device within the wireless local area network to determine whether some other device which provides a certain service is in adjacency of the first device, e.g. within the same room.
Computer terminals and peripherals have become dramatically smaller and more portable. Personal computers and peripherals are small enough to sit on the desk at work. Smaller still are lap top computers and notebook computers. There are computer terminals which are small enough to be mounted in a vehicle such as a delivery truck. Still smaller are the hand held terminals typically used for their portability features where the user can carry the terminal in one hand and operate it with the other. A physical connection of the above devices by means of cables or fibers might have drawbacks, such as configuration constraints because of the limited length of the cable, limited number of ports on the computer thus limiting the number of peripherals that can be attached, cumbersome reconfiguration of hardwired devices, etc. Note that there are some peripheral interface systems where the limited number of ports on the computer does not really limit the number of peripherals. Universal Serial Bus (USB) and IEEE 1394 (Firewire) are examples of peripheral bus systems capable of supporting a large number of devices on a single port. Ethernet is an example of a communication system where the cable is used as a shared medium (other examples are token ring, FDDI (Fiber Distributed Data Interface), and DQDB (Distributed Queue Dual Bus)).
The smaller the devices get, the more important it becomes to replace wired-based physical connections by wireless ad-hoc connections (e.g. body networks, radio frequency connections, or infrared connections), since physically connecting the computer terminals, peripherals, and other devices by means of cables or fibers severely reduces the efficiency gained by making the units smaller. Ad-hoc connections are required where devices move around, enter an area and exit the area. The term ad-hoc refers to the need for frequent network reorganization.
Local area communication is rapidly evolving into what can be called personal local area networks, which are networks for communication between local peers or subsystems. These kind of networks will herein be referred to as local networks. Wireless communication is of particular importance in such local networks. There are different wireless communications approaches known that have been developed and designed with an eye on the communication between peers or subsystems of such local networks.
GTE Corporation has developed a short-range radio-frequency (RF) technique which is aimed at giving mobile devices such as cellular phones, pagers and handheld personal computers (PCs) a smart way to interact with one another. GTE""s technique is tentatively named Body LAN (local area network). The original development of Body LAN was via a wired vest with which various devices were connected (hence the name Body LAN). This graduated to an RF connection a couple of years ago.
Xerox Corporation has developed a handheld computing device called PARC TAB. The PARC TAB is portable yet connected to the office workstation through base stations which have known locations. The PARC TAB base stations are placed around the building, and wired into a fixed wired network. The PARC TAB system uses a preset knowledge of the building layout and the identifiers of the various base stations to decide where a PARC TAB portable device is by the strongest base station signal. A PARC TAB portable device has a wireless interface to the base stations. The PARC TAB system assumes that the PARC TAB portable device is always connected to the network infrastructure. The location of each portable PARC TAB device is always known to the system software. The base stations establish regions and are connected to power supplies. PARC TAB communication systems have a star topology.
In an attempt to standardize data communication between disparate PC devices several companies, including Ericsson, IBM, Intel, Nokia, and Toshiba established a consortium to create a global standard for wireless RF-based connectivity between fixed, portable and mobile devices. There are many other adopter companies. The proposed standard comprises an architecture and protocol specifications ranging from the physical layer up to the application layer. The technology will for instance enable solutions to automatically synchronize application information kept in mobile devices with similar information kept in a fixed desktop computer when users enter their offices. Enabling seamless voice and data transmission via wireless, short-range radio, the Bluetooth technology will allow users to connect a wide range of devices easily and quickly, without the need for cables, expanding communications capabilities for mobile computers, mobile phones and other mobile devices. The Bluetooth operating environment is not yet fully defined, but there are expected to be similarities with the IrDA (Infrared Data Association) specification and the Advanced Infrared (AIr) specification. Other aspects that probably will find their way into Bluetooth might stem from the IEEE standard 802.11 and/or HIPERLAN, as promulgated by the European Telecommunications Standards Institute (ETSI).
Bluetooth radio technology provides a mechanism to form small private ad-hoc groupings of connected devices away from fixed network infrastructures. Bluetooth makes a distinction between a master unitxe2x80x94which is a device whose clock and hopping sequence are used to synchronize all other devicesxe2x80x94and slave units in the same network segment. In other words, the Bluetooth approach is centralized. A query-based discovery scheme is used for finding Bluetooth devices with an unknown address. Queries are also centralized at a registry server. It is a drawback of such a centralized approach that there is a central point of failure. It is another disadvantage of such a system that more overhead is required than in a distributed scheme. The main problem of such a system is in locating a single registry server, and what to do if it disappears. If a random two devices encounter each other they must first recognize each other""s presence, then decide which is the registry server, and then go about their business of communicating. It is this continual selection and re-selection of a leader that causes the increased overhead. The alternative is to expect users to carry one device that they always have with them, and make it always the leader.
This, however, is not always a practical option. Further details can be found in Haartsen, Allen, Inouye, Joeressen, and Naghshineh, xe2x80x9cBluetooth: Vision, Goals, and Architecturexe2x80x9d in the Mobile Computing and Communications Review, Vol. 1, No. 2. Mobile Computing and Communications Review is a publication of the ACM SIGMOBILE.
HomeRF (based on Shared Wireless Access Protocol (SWAP)) is another example of an operating environment which can be used to connect devices. A HomeRF Working Group was formed to provide the foundation for a broad range of interoperable consumer devices by establishing an open industry specification for wireless digital communication between PCs and consumer electronic devices anywhere in and around the home. The working group, which includes the leading companies from the personal computer, consumer electronics, peripherals, communications, software, and semiconductor industries, is developing a specification for wireless communications in the home called the SWAP. The HomeRF SWAP system is designed to carry both voice and data traffic and to interoperate with the Public Switched Telephone Network (PSTN) and the Internet; it operates in the 2400 MHz band and uses a digital frequency hopping spread spectrum radio. The SWAP technology was derived from extensions of existing cordless telephone (DECT) and wireless LAN technology to enable a new class of home cordless services. It supports both a time division multiple access (TDMA) service to provide delivery of interactive voice and other time-critical services, and a carrier sense multiple access/collision avoidance (CSMA/CA) service for delivery of high speed packet data. The SWAP system can operate either as an ad-hoc network or as a managed network under the control of a connection point. In an ad-hoc network, where only data communication is supported, all stations are equal and control of the network is distributed between stations. For time critical communications such as interactive voice, the connection pointxe2x80x94which provides the gateway to the PSTNxe2x80x94is required to coordinate the system. Stations use the CSMA/CA to communicate with a connection point and other stations. Further details about HomeRF can be found at the Home Radio Frequency Working Group""s web site www.homerf.org. The SWAP specification 1.0 is incorporated by reference in its entirety.
The above-mentioned IEEE 802.11 standard for wireless LAN medium access control comprises features for conserving power. At regular intervals, with small random time offsets, LAN members broadcast information about themselves only. If a device receives such a broadcast while it is preparing one itself, it will not broadcast that round. In this way, all devices broadcast their individual characteristics with statistically even distribution. Because the medium access control (MAC) layer is given specific addresses to which it directs transmissions, its image of the LAN does not always need to be up-to-date. It is a clear disadvantage of the approach promulgated in IEEE 802.11 that it might take some time until a newly arrived device or an absent device is announced/noticed. IEEE 802.11 LANs are centralized, star-shaped networks. It should also be noted that the 802.11 advertisements are only about communications characteristics and individual identity, not service offerings.
There are several more or less elaborate protocols and techniques that allow an ad-hoc wireless communication between mobile devices. The above described Bluetooth radio technology and HomeRF approach are prominent examples. All state-of-the-art protocols and techniques have certain drawbacks, as briefly addressed in the following section.
For seamless connection in an ad-hoc local network, the respective devices require a method for becoming aware (discovery) of the services offered by neighbours. In addition, the devices in such a network must make their own services known (advertisement). On one hand, the discovery and advertisement of services offered in a local network must be carried out in a timely manner, but on the other hand battery power must be conserved if portable devices are employed. It is a further requirement for a local network that entering the network is seamless such that the device can easily change locations. It is desirable that no user intervention is required if a device enters or leaves an ad-hoc network. It would be arduous if the user would have to push a button for every reconfiguration, for example. It is also desirable that a device should be able to leave the network without formal notification. A scheme for discovery and advertisement of services in a local network is described and claimed in co-pending European patent application entitled xe2x80x9cService Advertisements in Wireless Local Networksxe2x80x9d, filed on Jan. 25, 1999, currently assigned to the assignee of the present application.
In a local network environment adjacency-bound service provision can be crucial with certain applications. Application semantics may require or the user may desire that a particular service is furnished in the immediate spatial vicinity of the service-consuming device while for other services the location of the service-providing device is not relevant. Means must be provided that allow the requester of a service to ascertain that the service-providing device is in adjacency to the service-consuming device or the consumer himself/herself. Conventional service discovery schemes fall short of providing the service requester (service-consuming device) with the spatial information needed to make a semantically correct decision.
It is an object of the present invention to provide a scheme enabling adjacency-bound service distinction in a wireless local network.
It is an object of the present invention to provide a scheme for a service-consuming device, which is part of an ad-hoc wireless local network, to determine whether a service is rendered by a service-providing device which is in adjacency of the service-consuming device.
The present invention concerns a scheme for distinguishing services offered by a service-providing device in adjacency of a first device from services offered by a service-providing device not being in the first device""s adjacency. All devices are part of a wireless local network. The first device maintains a record with information about services and associated identifiers as well as a list of identifiers about service-providing devices. According to the present invention, the associated identifiers and the list of identifiers are compared to determine an associated service as being in adjacency of the first device if it is rendered by a service-providing device being listed in the list of identifiers. An associated service is determined as not being in adjacency of the first device if it is rendered by a service-providing device not being listed in the list of identifiers.
Furthermore, the present invention concerns an apparatus which is enabled for using a service offered by a service-providing device which is within the same wireless local network. The apparatus comprises a network interface for wireless communication with the service-providing device, and a service discovery module which maintains a record with information services and associated identifiers, and a list of identifiers about service-providing devices. The service discovery module enables the apparatus to distinguish a service offered by a service-providing device in adjacency of the apparatus from a service offered by a service-providing device not being in adjacency of the apparatus.
The present invention relates generally to wireless local networks and, more specifically, to a scheme which allows a service-consuming device within the local network to determine whether a particular service is rendered by a service-providing device within adjacency of the service-consuming device.
The present solution allows to combine a scheme for advertisement and/or discovery of services with a scheme for distinguishing services rendered by devices within adjacency of a service-consuming device from services rendered by devices which are not within its adjacency.
With the present invention, a solution is presented that, when used in combination with a wireless communications protocol, allows to ensure/control that certain services or tasks are carried out or assigned to devices which are within adjacency of the device which requests the service. According to the present invention a local network of all devices that are reachable, including those devices which cannot be reached directly but via one or more other devices, can be maintained, and inside this local network a smaller sphere (herein called adjacency) surrounding a service-consuming device (or user) can be defined. The notion of adjacency is herein used to help a service-consuming device to distinguish whether a service-providing device that renders a particular service is within the same area as the service-consuming device. I.e., one is able to select a service-providing device that is close to the user, or in the same room, for example.
The present scheme for distinguishing services can be used to define logical ad-hoc groups of devices within a local network, whereby such a group of devices includes all service-providing devices that are in adjacency of a particular service-consuming device.
Devices according to the present invention do not necessarily have to have identical implementations (from a software and/or hardware point of view) as long as at least the present scheme for distinguishing services is implemented in these devices.
The present scheme facilitates implementations where for example
a user or an application selects a service-providing device that is in convenient reach, e.g. a speaker that is close to the user;
a user or an application selects a service-providing device that is in the same room or bay of an open space office;
a user or an application selects a service-providing device that is allowed or enabled to handle classified information such as confidential or personal information;
a user or an application selects service-providing devices that offer a composite service and where at least the final input/output device that renders the composite service are in adjacency of the service-consuming device. Note that the intermediate devices of a service rendering device-chain need not be in adjacency of the service-consuming device.